California’s native fish face extinction

UC DAVIS (US) — Salmon and other native freshwater fish in California will likely go extinct within the next century due to climate change if current trends continue.

The study, published online in May in the journal PLOS ONE, assessed how vulnerable each freshwater species in California is to climate change and estimated the likelihood that those species would become extinct in 100 years.

The researchers from the Center for Watershed Sciences at the University of California, Davis, found that, of 121 native fish species, 82 percent are likely to be driven to extinction or very low numbers as climate change speeds the decline of already depleted populations. In contrast, only 19 percent of the 50 non-native fish species in the state face a similar risk of extinction.

Delta smelt are fifth on the list of native California fish most likely to become extinct in the state within 100 years due to climate change. (Credit: USFWS Pacific Southwest Region/Flickr)

“If present trends continue, much of the unique California fish fauna will disappear and be replaced by alien fishes, such as carp, largemouth bass, fathead minnows, and green sunfish,” says Peter Moyle, a professor of fish biology who has been documenting the biology and status of California fish for the past 40 years.

“Disappearing fish will include not only obscure species of minnows, suckers, and pupfishes, but also coho salmon, most runs of steelhead trout, and Chinook salmon, and Sacramento perch,” Moyle says.

Fish requiring cold water, such as salmon and trout, are particularly likely to go extinct, the study says. However, non-native fish species are expected to thrive, although some will lose their aquatic habitats during severe droughts and low-flow summer months.

The top 20 native California fish most likely to become extinct in California within 100 years as the result of climate change include (asterisks denote a species already listed as threatened or endangered):

Klamath Mountains Province summer steelhead

McCloud River redband trout

Unarmored threespine stickleback*

Shay Creek stickleback

Delta smelt*

Long Valley speckled dace

Central Valley late fall Chinook salmon

Kern River rainbow trout

Shoshone pupfish

Razorback sucker*

Upper Klamath-Trinity spring Chinook salmon

Southern steelhead*

Clear Lake hitch

Owens speckled dace

Northern California coast summer steelhead

Amargosa Canyon speckled dace

Central coast coho salmon*

Southern Oregon Northern California coast coho salmon*

Modoc sucker*

Pink salmon

The species are listed in order of vulnerability to extinction, with number one being the most vulnerable.

Climate change and human-caused degradation of aquatic habitats is causing worldwide declines in freshwater fishes, especially in regions with arid or Mediterranean climates, the study says. These declines pose a major conservation challenge. However, there has been little research in the scientific literature related to the status of most fish species, particularly native ones of little economic value.

Moyle saw the need for a rapid and repeatable method to determine the climate change vulnerability of different species. He expects the method presented in the study to be useful for conservation planning.

“These fish are part of the endemic flora and fauna that makes California such a special place,” says Moyle. “As we lose these fishes, we lose their environments and are much poorer for it.”

The California Energy Resources Conservation and Development Commission Instream Flow Assessment Program funded the study.